[Qgis-user] Removal of overlap geometries within the same layer - merge to largest neighbor polygon

[Bernhard Ströbl]

Hi Andreas,

the Algorithm "Eliminate selected polygons" was originally created to address these questions. I usually imported the data into GRASS ran a clean there and reexported the results into a non topolgical dataset. Thus overlapping areas and gaps (only if closed) are identified and can be eliminated using the algorithm named above (selecting only a certain area-circumference relation) by merging it with the adjacent polygon with the smallest/largest area or the longest common boundary.
For your case you could have used this algorithm after the union to identify overlaps.
As for an algorithm that does all this in one go: You would need something that detects holes between polygons without the help of a toplogical data format. 

regards
Bernhard

> Andreas Neumann via QGIS-User <qgis-user at lists.osgeo.org> hat am 25.07.2023 12:01 CEST geschrieben:
> 
>  
> Hi,
> 
> A friend of mine has a dirty input data set with lots of overlapping 
> geometries (within the same layer) and asked me if there is a tool 
> within QGIS to automatically remove the overlaps and assign the 
> overlapping area to the neighbor polygon with the largest area.
> 
> The solution was surprisingly hard to find, although I am pretty sure 
> there are multiple combinations of algorithms that would solve the 
> problem. Here is the solution I came up with: 
> https://github.com/qgis-ch/overlap_removal/tree/main [1]- perhaps you 
> have better ideas - more elegant solutions?
> 
> Wouldn't it be great if QGIS had a processing tool to solve this overlap 
> cleaning within the same layer "out of the box" without having to use a 
> graphical model or a more or less complicated sequence of algorithms in 
> the processing toolbox? Apparently, ArcGIS has such a tool ...
> 
> Saga and GRASS also might have such tools - but I couldn't get the SAGA 
> based QGIS plugin "Dissect and dissolve overlaps" 
> (https://plugins.qgis.org/plugins/dissect_dissolve_overlaps).
> 
> The same problem exists for automatically filling small gaps in the 
> polygon data set ...
> 
> Andreas
> 
> 
> 
> Links:
> ------
> [1] https://github.com/qgis-ch/overlap_removal/tree/main_______________________________________________
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